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# Magnesium Sulphate
## Overview
Magnesium sulphate is an electrolyte that plays a crucial role in various enzymatic and physiological functions. It can be administered intravenously or intramuscularly.
## Primary Indications
* **Eclampsia/Pre-eclampsia:** Management and prevention of seizures.
* **Hypomagnesemia:** Treatment of low serum magnesium levels.
* **Torsades de Pointes:** Management of polymorphic ventricular tachycardia.
* **Bronchodilation:** Adjunctive therapy in severe asthma exacerbations.
## Adult Dosing
* **Eclampsia/Pre-eclampsia (Treatment):** Loading dose: 4-6 grams IV over 5-20 minutes. Maintenance dose: 1-2 grams/hour IV infusion.
* **Eclampsia/Pre-eclampsia (Prophylaxis):** Loading dose: 4 grams IV divided into two doses (2g each) administered over 5-20 minutes. Maintenance dose: 1 gram/hour IV infusion.
* **Hypomagnesemia:**
* **Severe (serum Mg < 1.5 mEq/L):** 4-6 grams IV infused over 4-6 hours, may repeat every 4 hours as needed.
* **Mild to Moderate (serum Mg 1.5-2.5 mEq/L):** 2-4 grams IV infused over 4-6 hours.
* **IM administration:** 1 gram IM every 4-6 hours for 4 doses.
* **Torsades de Pointes:** 1-2 grams IV bolus in 10-20 mL of D5W over 5-10 minutes, followed by an infusion of 0.5-1 gram/hour.
* **Asthma Exacerbation:** 1-2 grams IV in 50-100 mL NS or D5W over 15-30 minutes.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing is highly variable and often based on local protocols. A common guideline is 25-50 mg/kg/dose IV over 1-4 hours. Maximum dose generally not to exceed 2 grams per dose.
* **Eclampsia/Pre-eclampsia:** Limited data for pediatric use; typically follows adult guidelines if indicated.
* **Asthma Exacerbation:** 25-50 mg/kg IV over 15-30 minutes. Maximum dose generally not to exceed 2 grams per dose.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Significant impairment may require reduced dosage and increased monitoring due to risk of accumulation.
## Contraindications
* Heart block
* Myocardial damage
* Hypermagnesemia
## Adverse Effects
* **Common:** Flushing, hypotension, somnolence, decreased deep tendon reflexes.
* **Serious:** Respiratory depression, cardiac arrest, hypermagnesemia.
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** May potentiate neuromuscular blockade.
* **Calcium Salts:** Can antagonize the effects of magnesium.
* **Nifedipine:** Potential for additive hypotension and neuromuscular blockade.
## Monitoring
* **Serum Magnesium Levels:** Monitor frequently, especially with continuous infusions or in renal impairment. Target levels vary by indication.
* **Vital Signs:** Blood pressure, heart rate, respiratory rate.
* **Deep Tendon Reflexes:** Assess for diminished reflexes, a sign of toxicity.
* **Urine Output:** Monitor for adequate renal function.
* **ECG:** Monitor for changes indicative of hypermagnesemia (e.g., prolonged PR, QRS, QT intervals).
## Clinical Pearls
* Magnesium sulphate administration can lead to hypotension, hence monitor blood pressure closely and administer infusions slowly.
* Calcium gluconate (1 gram IV) is the antidote for magnesium toxicity.
* Always ensure adequate renal function before administering magnesium sulphate, especially in higher doses.
* For eclampsia, therapy should be continued for at least 24 hours after the last seizure or birth.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines for definitive patient care decisions.*
